1. Field of the Invention
The present invention relates to a process for preparing block copolymers which are useful as functional polymers such as surface modifiers of polymeric materials, compatibilizers of polymer alloys and materials for coatings and membranes, as well as novel block copolymers prepared therefrom. More particularly, the present invention relates to a process for preparing novel block copolymers containing a (meth)acrylic ester as one of the segments and the novel block copolymers prepared therefrom.
2. Description of the Prior Art
Block copolymers containing polymer chains A and B of different structures which are connected in the form of A--B or A--B--A provide characteristics of both the polymer chain A and the polymer chain B. Consequently, it has been known that block copolymers have good prospects as functional polymers such as surface modifiers, compatibilizers and materials for coatings and membranes. However, the synthesis of block copolymers itself is not easy and, in particular, there is almost no method for mutually connecting polymer chains having quite different properties. Accordingly, the practical use of block copolymer has been considered to be difficult.
For example, even in anion living polymerization, which is most commonly used for the synthesis of block copolymers, monomer types which are capable of polymerization are limited. As a result, block copolymers have not yet been in practical use except for styrene-dien base block copolymers. An attempt has also been tried to prepare block copolymers by radical polymerization in the presence of polymeric peroxides. The polymeric peroxides, however, are dangerous to handle and cannot precisely control the structure of the resulting polymers and hence have not yet been employed for practical utilization. Additionally, synthesis of block copolymers has been tried by reacting high-molecular compounds with each other. However, since reaction conditions such as selection of a common solvent are difficult to set and efficiency of block polymerization is low as well, this process has also not yet been applied to actual production.
As a means for the synthesis of block copolymers, Japanese Patent Laid-Open No. 13603 (1983) disclosed a so-called group transfer polymerization method. The method described in the specification is effective in practical use only for acrylic monomers such as methacrylic esters and acrylic esters. Thus, when the polymer chains have quite different structures, synthesis of block copolymer by connecting the polymer chains with each other is also deemed to be difficult in this method.